Tensioner for continuous web rewind roll

ABSTRACT

A tensioner for controlling tension in a continuous web being wound onto a rewind roller after the web is processed, for example after printing on labels carried on the web. The tensioner receives the web from a processor and has a slack sensor between the processor and the input of the tensioner. The slack sensor indicates when the slack is a selected minimum, and the web is clamped by the tensioner. After a selected time, which is before the slack sensor indicates a maximum slack is present, the motor driving the rewind roller is stopped and the web is unclamped. After unclamping the web, the rewind roll is again driven at a speed to take up more of the web than that which is driven by the processor, to wrap the web around the core until the slack sensor indicates the slack in the web is at a minimum.

BACKGROUND OF THE INVENTION

The present disclosure relates to a system for controlling the tensionon a web that is being wound onto a rewind roll from the output of aprocessor, such as a printer, through which the web has passed. The webis a continuous strip that may carry labels or other materials that areprinted.

Label printers, in particular, have a supply roll of a continuous web orsubstrate carrying the labels and the web is fed through the printer.After the label is printed, the web is wound onto a rewind roll so thatthe printed labels can be removed from the web for use. It is importantthat the web is tightly wound on the rewind roll. It is desirable thatthe web is not pulled by external tension as it passes through theprinter, to avoid printing problems. Also, the web should be wound sothat the rewind roll has a smooth, uniform edge.

SUMMARY OF THE INVENTION

The present disclosure relates to a web rewind system for controllingthe tension with which a web or substrate is rewound onto a roll. Therewinding is done in a manner that ensures the web or substrate istightly wound on the rewind roll, and which also ensures that thetension in the web at the rewind roll does not cause external tension onthe web portion that is in the processor or printer. It is known to havean adjustable torque drive on a web rewind roll so that the amount oftension created in a web being wound onto the rewind roll can becontrolled.

The present device is a web control that will receive the web after theweb has passed through a processor, as shown a printer, and before theweb is wound onto a rewind roll, so that periodically the web can beclamped and the loops of the web on the rewind roll are tightened downonto the core by driving the core without causing any increase intension in the web as it exits the printer. The present rewind tensioncontrol device is compact and easy to use, and the web can be tightlywound on the rewind roll with a lower initial wrap tension than withprevious tension controls. Temporarily clamping the continuous web orsubstrate and controlling the motor driving the rewind roll to continueto rotate creates tension in the web between the clamp point and therewind roller, and web material previously wound or looped on the rolltightens on itself. Preferably, only a short length of web material ispermitted to wrap loosely onto the rewind roll before clamping andtightening, so the slack in the form of loose loops on the rewind rollis easily taken up.

Rewind rolls can be wound with a web until the roll is quite large, forexample, up to a twelve inch outside diameter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevational view of a typical printer for printing on alabel held on a continuous substrate or web, and having a rewind rollpositioned to receive the web from a tensioner made according to thepresent disclosure;

FIG. 2 is a sectional view of the tensioner and rewind roll taken alongline 2-2 in FIG. 6 with a web clamp in an open position;

FIG. 3 is a view taken on the same line as FIG. 2, with a web clamp in aclamping position;

FIG. 4 is a side elevational view of the tensioner of FIG. 2 taken froman opposite side of that shown in FIG. 1;

FIG. 5 is an enlarged view of the mounting of a slack sensing arm andsensor shown in FIG. 4; and

FIG. 6 is a view taken along line 6-6 in FIG. 1 with parts removed toshow inner workings of a web clamp.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

FIG. 1 illustrates an overall side view of a printer 10 that prints ontoitems such as labels held on a continuous substrate or web 12 unwoundfrom a supply roll 14, and utilizing a rewind roll web tensioner 28 ofthe present disclosure. As shown, printer 10 of conventional design isprovided with the web or substrate 12 carrying items to be printed, suchas labels, and the web is removed from a supply roll 14 mounted on asuitable support 16. The web 12 is fed across a printer infeed section18, into the interior of the printer 10 to pass under a print head shownschematically at 20. The web is driven by at least one pair of printerfeed rolls 22, which are driven by a motor 24 that is part of theprinter control system which is controlled by a programmable printercontroller 26.

The web 12 is fed from the feed rolls 22 to exit the printer 10, andthen it passes to an input of web tensioner 28, and then is wound onto arewind roller assembly 30 that includes a central core 32 on which theweb is wound. The core 32 is supported on a mandrel 31.Side guide plates33 of roller assembly 30 are spaced apart and supported on the mandrel31. The web fits between guide plates 33. The rewind roller assembly 30is driven by a suitable variable torque output motor shown schematicallyat 34. The output torque of motor 34 is electronically adjustable in aknown manner, so that the drive torque for the core 32 can be adjustedfrom a torque adjustment control 36. Adjustable torque output motors arecommercially available.

The tensioner 28 includes guides for guiding movement of the web, andhas a “dancer” roll, or slack sensing roll, held in a slack sensorassembly 38. The slack sensor assembly 38 includes a pair of pivotingarms 40, as can be seen in FIG. 5 for example, and a free rolling dancerroll 42 mounted onto and extending between the outer ends of the arms40. The arms 40 are pivotally mounted on suitable shafts 44 to sidewalls of a housing 46 for the tensioner.

The dancer roll 42 moves up and down as the slack of the web lengthbetween the printer and an infeed to the tensioner forming a loop 13changes, causing the arms 40 to pivot from an upper operational positionshown in solid lines in FIG. 2 to a lower operational position shown indotted lines in FIG. 2. The slack sensor assembly 38 thus senses theslack in the web 12 at the input or infeed side of the tensioner 28 asthe slack loop 13 moves between these two positions. The arms 40 androller 42 are not spring loaded, and gravity provides the amount offorce needed for sensing slack in the web 12.

As can be seen in FIG. 2, the web 12 is fed to an input side or infeedof the tensioner and into the interior of the tensioner housing 46, andpasses over a first idler guide roller 48 that is rotatably mounted onthe side walls of the housing 46 on suitable bearings. The first idlerguide roller 48 is also shown in FIG. 6.

The web 12 passes underneath a guide plate 52, and underneath an upperclamp pad 54 that is carried by a portion of the guide plate 52. Theguide plate 52 is held in the housing in a suitable manner.Additionally, there are guide plates 56 in the housing 46, that, whilethreading the web, guide it along the bottom side of a second idlerguide roller 58 that is also suitably rotatably mounted between sidewalls of the housing 46. A lower guide plate 60 is provided below theweb 12 to guide the web if it is slack, while threading the web. Therollers 48 and 56 define the path of the web when the web is undertension while winding or tightening the web on the rewind roll.

The upper clamp pad 54 operates in connection with a lower clamp pad 62that is below the web 12, and aligned with the upper clamp pad 54. Theclamp pads together form a web clamp or web restraint that preventslongitudinal, lineal movement of the web 12. The guide plate 52 and theupper clamp pad 54 extend transversely between the side walls of thehousing 46.

The lower clamp pad 62 likewise extends across the tensioner between theside walls of the housing 46 and is formed as part of a plate-like lowerclamp pad bracket or plate 64 that is slidably guided for limitedvertical movement. As can be seen in FIG. 6, the lower clamp pad bracket64 is spring loaded in an upward direction tending to move the lowerclamp pad 62 toward the upper clamp pad 54, using suitable springs 66 onopposite ends of the bracket 64. It can be seen that the lower clamp padbracket has slots that are guided along suitable guides 68 held relativeto the housing 46.

The lower clamp pad bracket 64 is spring loaded toward the upper clamppad 54 with springs 66 to a web clamping position. A cam 70 that isdriven from an output shaft 80 of a clamp motor 82 can be rotated tomove the lower clamp pad 64 to an open position. The cam 70 aligns witha flange 84 that is formed on the clamp pad bracket 64, so that as motor82 rotates the cam lobe will engage the flange 84 and move the lowerclamp pad bracket 64 against the force of the springs 66 to the openposition that is shown in FIG. 2 with the lower clamp pad 62 spaced fromupper clamp pad 54. When the cam 70 is rotated so it moves away from theflange 84 the springs 66 urge the lower clamp pad 62 against theunderside of the web 12 to push the web 12 up against the upper clamppad 54 in a web clamping position shown in FIG. 3.

When the web 12 is clamped as shown with the clamp pads in the positionof FIG. 3, the web 12 on the input side of the tensioner 28 cannot bemoved to be rewound onto the rewind roller, but is held securely. Whenthe rewind roller is driven by the torque adjustable motor with the webclamped, any loose loops of web will be tightened down onto the core 32and previously tightened loops of web 12 forming a rewind roll, and atension is created in the web 12 between the clamp 61 and the loops ofthe web on the rewind roller core 32. Therefore, any loose loops on thecore or on a partially formed roll of web material will be drawn tight,to form a tight winding around the core 32 as a function of the torqueof motor 34 driving the core. It can be seen that since the clamp pads54 and 62 operate to securely hold the web, any tension in the webbetween the clamp 61 and the rewind roller 30 will not increase thetension on the length of the web 12 between the printer 10 and thetensioner 28 which forms slack loop 13. This means that any tension loadfrom driving the rewind roll will not tend to pull the web through theprinter, which can disrupt the printing function and cause misprints.

The desired positions of the dancer roll 42 are sensed to providesignals indicating a desired minimum and maximum slack in the web lengthbetween the printer output side and the tensioner. When there is slackless than the minimum, the rewind roller will continue to rotate afterthe clamp pads 54 and 62 separate until the roll 42 reaches an upperoperational position where the slack at the infeed of the tensioner is aminimum. When the web is clamped and the rewind roll is tightened, theslack will increase because the web continues to be driven through theprinter, and the dancer roll will reach a lower operational positionwhere the slack loop 13 is at an operational maximum. The rewind rolleris driven at a speed to provide a lineal speed of movement of the webgreater than the lineal speed of movement of the web through the printerto reduce the slack in the web length between the printer and the infeedof the tensioner during operation when the web is unclamped. The dancerroll 42 will then move between the two different operational positionsof arms 40, including the lower operational position (maximum slack)which is illustrated in dotted lines in FIGS. 2 and 3, and an upperoperational position indicated in solid lines in FIGS. 2 and 3, which isreached as the slack reduces while the rewind motor is running and theweb is unclamped.

When the tension in the web 12 between the printer 10 and the tensioner28 is such that the web lifts the dancer roll 42 to the position shownin solid lines in FIG. 2, the rewind motor will be stopped and the clamp61 closed. Once the clamp 61 is closed, the rewind motor 34 is startedagain to tighten the web lengths or loops on core 32. The printercontinues to drive the web toward the tensioner, so the slack loop 13increases in size while the rewind roll is tightened, and the dancerroll 42 thus moves down.

The two operational positions of the dancer roll 42 are sensed by armposition sensors shown in FIGS. 4 and 5. One end of shaft 44 carries asensor target disc 90 that is in the form of a part circular disc. Thetarget disc 90 is associated with two individual sensors, 92 and 94,mounted on the tensioner to signal selected pivotal positions of thearms 40. The sensors are each optical sensors that have a light sourceand a receiver that are spaced apart, and the disc 90 will pass betweenthe light source and receiver of each sensor as the arms 40 move betweensensed low and high positions. The sensors include a low operationalposition sensor 92 and a high operational position sensor 94 to providesignals when the sensor beam from the respective sensor is no longerblocked by the disc 90. In other words, the edges of the disc 90determine the sensed arm positions. As shown in FIG. 5, the disc 90 andthe arms 40 are in the dancer roll low operational position, and theedge 90B of disc 90 (behind the one part of sensor 92 in FIG. 4) hasunblocked the beam from the light source of sensor 92 from the receiverof that sensor, or in other words has permitted light to strike thereceiver. The sensor 94 senses when an edge 90A of the disc 90 hasunblocked the sensor beam of sensor 94 so the light will strike itsreceiver as the arms 40 move up in direction as indicated by arrow 96 inFIG. 4. Signals are thus provided to controller 37 indicating the twooperational positions of the arms 40 and dancer roll 42.

Additionally, the clamped and operational positions of the lower clamppad 62 and the lower clamp pad bracket 64 are sensed by a sensor 98 thatprovides a signal when a flag 100 attached to the lower clamp padbracket 64 is aligned with the sensor. The signal indicating theposition of the bracket 64 and the lower clamp pad 62 is provided to acontroller 37 to indicate whether the web 12 is clamped or free to move.The controller 37 controls the interaction of web tensioner 28 and theoperation of the rewind motor 34.

When the printer and rewind system shown in FIG. 1, for example, is tobe loaded with a web 12 carrying printer labels, which are provided froma supply roll 14, the printer 10 can be threaded in a normal manner. Thearms 40 and the dancer roll 42 are moved to an inoperative raisedposition which is shown by the dotted lines in FIG. 1. In this position,the edge 90A of flag or disc 90 is moved away from the light beam of thesensor 94 and the receiver of the sensor provides a signal so a sectionof a timer 35 will start timing. If the light is still received by thereceiver after a selected sensor time period, for example 8 to 10seconds, the drive motor 34 for the rewind roll is stopped by controller37 and not started again until the arms 40 are moved back to operatingpositions. The cam 70 also is moved under control of controller 37 toits position so clamp 61 is open and not clamped.

The continuous web or substrate 12, such as label stock, is threadedthrough the tensioner, as shown in FIG. 2, over the guide roller 48,between the upper and lower clamp pads 54 and 62, and under the guideroller 58. The end of the web is fastened in a suitable manner to thecore 32 of the rewind roller.

When this is done, the arms 40 and the dancer roll 42 are moved toengage the web 12, which forms a slack loop 13 and the sensor 92indicates the disc 90 is no longer blocking its light beam, the rewindsystem can be operated. The movement of the arms 40 to the loweroperational position will thus automatically start the rewind motor 34through the controller 37, to wrap the web around the core 32 at a speedfaster than the web is fed out of the printer or other device with whichthe tensioner is used. The web 12 is moved so that the slack loop 13lifts the dancer roll 42 high enough so that the position sensor 94signals that the dancer roll 42 is in the upper operational position.The rewind motor will be stopped by the controller 37 in response tothis signal, and the tensioner clamp motor will be started to drive thecam 70 so the lower clamp pad bracket is moved upwardly under the springload from springs 66 until the flag 100 moves far enough so that thelower clamp position sensor 98 indicates to the controller that theclamp bracket 64 is raised. At this point, the lower clamp pad 62 willhave moved web 12 against the upper clamp pad. This clamps the web andholds it in position, as shown in FIG. 3. The clamp used is to hold orrestrain the web that is coming from the printer from longitudinalmovement so it does not wind around the outside of the rewind roll.

The variable torque motor 34 for the rewind roll 30 will then be turnedon, thereby tightening the coils or loop of the web that have beenloosely wrapped around the core 32, by allowing the core to be rotatedand the wraps of web to slip upon themselves and tighten onto the coreas the web is held from longitudinal movement by the clamp 61.

The rewind motor 34 is timed as it runs to tighten the loops or wrapswith a section of timer 35 in controller 37, and after the clamp 61 isclosed, the motor 34 will run for a set period of time, which isdependent upon the speed of the web 12 as it is fed out of the printer10, and the movement or pivoting of the arms 40 for the dancer roll. Thetime period for running motor 34 for tightening the wraps or coils ofthe web on the core is set so that the rewind motor will stop before theweb length between the printer and tensioner forming slack loop 13,which is being fed by the printer, becomes slack enough for the dancerarms 40 and roller 42 to reach the lower operational position, as sensedby the sensor 92. In a typical system the tightening time of running themotor 34 may be under 1 second. While, as shown, the motor 34 stopsafter a set period of time, the motor also could be stopped by a thirdsensor sensing the position of the arms 40 to signal when the arms arenear, but not yet at, the lower operational position.

When the rewind motor 34 is stopped by controller 37 after the set timeperiod for tightening the web loops or wraps on the rewind roller (orafter a signal from a third sensor), the tensioner clamp motor 82 willbe started by the controller to turn the cam 70 to release the clamp 61.The sensor clamp position sensor changes states again, as sensed by theflag 100 and the sensor 98. The cam 70 will have moved the lower clamppad 62 away from the upper clamp pad 54 to the position shown in FIG. 2to release the web.

After the cam 70 has moved the lower clamp pad 62 away from the upperclamp pad 54, and the rewind motor has not yet started again, the slackloop 13 increases and a signal from sensor 92, indicating the dancerroll 42 has reached it lower operational position will be received bythe controller 37. Motor 34 for the rewind roll will again be started towind the web fed from the printer around the rewind roller core at alineal speed of the web greater than the lineal speed of the web fedfrom the printer, until the web slack loop 13 reduces and the web againlifts the dancer arms 40 and the dancer roll 42 high enough so thedancer roll upper operational position sensor 94 provides an upperposition signal to the controller. The clamp motor 84 will again beenergized to turn the cam 70 to permit the lower clamp pad 62 to move upagainst the upper clamp pad 54 under the spring force to hold orrestrain the web or substrate from moving, and the process then repeats.

While the present discussion has dealt with a web that is carryinglabels to be printed, and used in combination with a printer, thetensioner can be utilized for controlling rewind tension in a continuousweb regardless of what process the web undergoes, to ensure that acontinuous web is wound efficiently onto a rewind or take up roller. Therewind roller is capable of exerting a set tension in the web, basedupon the output torque of the motor that is driving the rewind roller,in order to have the loose loops or wraps periodically tightened downonto the core and any previous wound wraps forming the rewind roll. Thisinsures a tight rewind roll, and keeps the roll usable for easilyremoving labels or other items that might be on the web that has beenre-wound.

The system is preferably set so that when the rewinding is firststarted, and the rewind roll of printed web is small, only approximately12 inches length of the web will be passed through the tensioner beforethe web is clamped and the rewind roller tightens the loose loops orwraps down onto the core. The function of restraining the web fromlongitudinal lineal movement and tightening down the lengths of the webforming loops or wraps on the rewind roll in short intervals insuresthat the web will not have to be placed under excessive tension in orderto try to tighten down several loops or wraps of the web on the rewindroller, especially if the web is non-slippery in nature. As the rewindor take-up roll of web and printed labels gets larger, the clamping orrestraining of the web to permit tensioning the web wrapped on therewind roll can be activated and the rewound web tightened before a fullwrap is made on the rewind roll. The wraps of web are thus kept tightwithout exerting a high torque on the rewind roller.

The dancer roll 42 is illustrated as being mounted on two pivoting arms,but can be mounted to cantilever from one arm, or can be mounted in aguide or guides to slide up and down between its desired positions as itsenses slack in the web between the printer and the tensioner 28.

When there is no web present at the infeed of the tensioner 28, that isbetween the printer and the tensioner, the dancer roll 42 and arms 40will move to or past the lower operational position and the edge 90B ofdisc 90 clears the lower operational position sensor 92 so light fromthe sensor light source is received by the receiver of the sensor, andagain the controller 37 and a section of timer 35 would time how longthe light source of sensor 92 was received by its receiver, and if thebeam of light was not blocked by the disc 90 after a selected sensortime period for sensor 92, for example, again, 8 to 10 seconds, themotors 34 and 82 would be kept off by controller 37 until the tensioningsystem was reloaded with a web. The sensor time period for sensor 92 canbe different from the sensor time period for sensor 94, if desired.

While a direct acting clamp 61 is disclosed as the web restraint, otherweb restraints that prevent movement of the web to hold the web fromwrapping around the rewind roll, and which will permit rotating therewind roll core after the web movement is restrained, can be used.

Although the present invention has been described with reference topreferred embodiments, workers skilled in the art will recognize thatchanges may be made in form and detail without departing from the spiritand scope of the invention.

1. A tension control device for a continuous web to be wound onto a rollhaving a motor for rotatably driving the roll for winding the web, thetension control device comprising: a web restraint operable to preventmovement of the web; a control to initiate the motor to drive the rollto tighten portions of the web on the roll when the web restraint isoperated to prevent movement of the web; and a release mechanism torelease the web restraint to permit movement of the web when the roll isrotatably driven by the motor.
 2. The tension control device of claim 1including a processor to drive the web to an infeed of the tensioncontrol device, a web slack sensor sensing slack in the web being drivento the infeed, the web restraint being operated for preventing movementof the web when the web slack sensor indicates a selected slack in theweb, and a second sensor to provide a signal starting the motor fordriving the roll when the web is prevented from movement.
 3. The tensioncontrol device of claim 2 wherein the web slack sensor provides a secondsignal indicating that the slack in the web is a selected maximum, themotor being timer controlled to stop driving the roll before the webslack sensor provides the second signal.
 4. The tension control deviceof claim 2, wherein the processor drives the web to the infeed at afirst lineal speed, and the motor drives the roll at a speed to providea lineal speed of the web greater than the first lineal speed when theweb restraint is released.
 5. The tension control device of claim 2,wherein the web slack sensor comprises a rotatable sensing roll mountedto move relative to a path of movement of the web between the processorand the infeed, said sensing roll being moved by the web between a firstposition indicating at least a reduced slack in the web, and a secondposition indicating a maximum desired slack in the web.
 6. The tensioncontrol device of claim 5, wherein said sensing roll is mounted on anarm, said arm being pivoted relative to the tension control device topermit the sensing roll to move in an arc as the sensing roll movesbetween the first and second positions.
 7. The tension control device ofclaim 1, wherein the web restraint comprises clamp pads that are spacedapart, with the web passing between the clamp pads, and wherein therelease mechanism moves one of the clamp pads away from the other clamppad.
 8. A tension control device of claim 1 further comprising a timerto control the motor to rotate the roll for a set period of time afterthe web restraint has been operated to prevent movement of the web. 9.The tension control device of claim 1, and further comprising acontroller receiving a signal indicating that a web length at an infeedof the tension control device is slack and thereafter operating therelease mechanism to release the web restraint and to start the motor todrive the roll.
 10. The tension control device of claim 9 including aweb slack sensor providing a signal to the controller when the slack inthe web length at the infeed of the tension control device is at aselected minimum, to operate the clamp to prevent movement of the web,and to initiate the motor to drive the roll to tighten portions of theweb on the roll.
 11. The tension control device of claim 9 wherein saidmotor drives the roll, after the web restraint is released by therelease mechanism such that the web moves at a lineal speed whichreduces slack in the web length at the infeed of the tension controldevice.
 12. The tension control device of claim 1, wherein said webrestraint comprises a clamp and further comprising guides for guidingthe web through the clamp and to the roll.
 13. A tension control systemfor regulating the tension in a continuous web as the web is wound ontoa rewind roll from a printer driving the web, the printer having a webfeed driving the web through the printer, the tension control systemincluding a tensioner assembly between the printer and the rewind rollassociated with the web, said tensioner assembly having a slack sensorfor sensing slack in the web between the printer and the tensionerassembly, and a web restraint to prevent movement of the web around therewind roll, a motor to drive the rewind roll to rewind a web thereonwhen the web restraint is positioned to permit movement of the web, andto tighten the web onto the roll at selected intervals when the web isprevented from movement around the rewind roll.
 14. The tension controlsystem of claim 13, and a slack sensor operable to sense a slack in theweb between the printer and the tensioner assembly, sensors to sense aposition of the slack sensor indicating the amount of slack in the webbetween the printer and tensioner assembly, and a controller toperiodically cause the motor to drive the rewind roll to rewind the webonto the rewind roll when the web is permitted to move by the webrestraint, and to cause the motor to rotate the rewind roll to tightenloose lengths of the web on the rewind roll when the web is preventedfrom movement from the printer to the rewind roll.
 15. The tensioncontrol system of claim 13 wherein said web restraint comprises a clampand further comprising a clamp control to release the clamp and permitthe web to be rewound on the rewind roll when the slack in the webbetween the printer and the tensioner assembly is indicated as being aselected amount, and to operate the clamp to clamp the web when theslack sensor indicates when the slack of the web between the printer andthe tensioner assembly is at a selected minimum amount.
 16. The tensioncontrol system of claim 13, wherein said web restraint comprises aclamp, a spring to spring load the clamp to a clamping position torestrain the web, and a release mechanism to release the clamp againstthe spring load in response to a signal from the slack sensor.
 17. Amethod of controlling wrapping of a an elongated web onto a rewind roll,comprising driving the web longitudinally lineally from a processor,providing a driven rewind roller to take up the elongated web from theprocessor, providing a web restraint to selectively restrain the webfrom longitudinal lineal movement, periodically restraining the web anddriving the rewind roller while the web is restrained to tighten lengthsof the web previously wound on the rewind roller.
 18. The method ofclaim 17, including sensing slack of the web between the processor andthe web restraint to provide signals to selectively restrain and releasethe web for longitudinal lineal movement at selected intervals.
 19. Themethod of claim 18 including driving the rewind roller at a speed suchthat the web has a lineal speed when the web is released that is greaterthan a lineal speed of the web as driven by the processor.
 20. Themethod of claim 17 including providing a clamp for forming the webrestraint, sensing slack of the web between the processor and the clampand clamping the web with the clamp to restrain longitudinal linealmovement of the web when slack of the web between the processor and theclamp is a selected minimum.
 21. The method of claim 20 includingsensing when slack of the web between the processor and the clamp is ata selected maximum after the web is clamped by the clamp, stopping thedrive to the rewind roller prior to the time slack of the web reachesits selected maximum, and releasing the clamp to permit the web to movewhen the selected maximum slack is sensed.
 22. The method of claim 21and further comprising driving the rewind roller after the clamp isreleased until slack of the web between the processor and the clamp issensed to be at the selected minimum.